Vertically integrated hybrid components having at least one MEMS element and at least one ASIC element are of particular significance, the micromechanical and electrical functions of which complement one another. The micromechanical structure of the MEMS element may be used to detect mechanical variables, such as accelerations, rotation rates, or pressure, or also as an actuator, for example, in the form of an activatable valve or loudspeaker. The ASIC element advantageously includes circuit means for measuring signal processing and analysis or for activating the MEMS actuator function.
It is known that the individual elements of a vertically integrated hybrid component may be joined together by bonding to form a chip stack. Both mechanical and also electrical connections are generally established between the part components. Bonding methods additionally enable the implementation of hermetically sealed connections. This is frequently utilized in practice to cap the micromechanical structure of a MEMS element using the ASIC element and thus protect it against environmental influences.
Preferred bonding methods for the construction of vertically integrated hybrid components are silicon direct bonding and eutectic bonding. In these bonding methods, the two wafers to be connected are pressed against one another at an elevated temperature. Wafer bows and surface roughness are compensated for by a relatively high contact pressure. Since this contact pressure is only introduced via the bond contact points into the elements to be connected, the bonding process results in an uneven pressure load of the individual chip areas. This has proven to be problematic in particular for the ASIC element. Specifically, during the ASIC processing, the material of the dielectric insulation layers of the ASIC layer structure is optimized with regard to a preferably low dielectric constant, to minimize RC delays in the printed conductors of the wiring levels. Since the dielectric constant is lower the more porous the dielectric material is, mechanically fragile materials are increasingly being used for the insulation layers of the ASIC layer structure. The risk therefore exists that the functional elements of the ASIC element will be damaged during the bonding process as a result of the low mechanical stability of the individual layers of the ASIC layer structure.